1. Field of the Invention
The present application relates to a transmitter optical module that outputs an optical signal containing two or more wavelengths.
2. Related Background Art
Recent optical communication has continuously requested to increase the capacity thereof drastically. Conventional systems, such as the full-duplex system, do not give a satisfactory solution for the request above. One practical solution is the wavelength division multiplexing (WDM) system where two or more optical signals each having a specific wavelength different from others are wavelength multiplexed and thus multiplexed optical signal is transmitted through a single fiber. The QSFP+ standard, which is one of multi-source agreements for a pluggable optical transceiver, has ruled that four optical signals each having a wavelength in 1.3 μm band and a transmission speed of 10 Gbps or 25 Gbps are multiplexed to realize a total speed of 40 Gbps or 100 Gbps.
Japanese Patent Applications published as JP-H07-336037 and JP-2000-151012 have disclosed another type of such optical transceivers with the wavelength multiplexing function. The optical source that multiplexes the wavelengths inherently needs, as described above, a plurality of optical sources each being controlled in optical output power thereof by, for instance, automatic power control (APC) circuit. When optically active devices, half of which emit optical signals; while, the rests monitor respective optical output power, are concurrently installed in a housing, entanglement between the light emitting devices and light receiving devices becomes a problem. In order to control the output power of the specific light emitting device, the precise and accurate monitoring of the optical power output therefrom becomes inevitable.
However, a request to make the size in compact is always raised even when an optical transceiver has the wavelength multiplexing function, which inevitably causes the accuracy of the monitored output power of the optical sources. That is, when the optical output of a target device is to be monitored, the devices except for the target device always influences the monitored output power, which degrades the accuracy of the detection and causes the poor control of the optical output power.